As here circumscribed the family Pteridaceae is treated in a broad sense as to include (among others) Adiantaceae, Cryptogrammaceae, Hemionitidaceae and Sinopteridaceae, in accordance with updated phylogenetic research (see for instance Smith & al. 2006). The family thus defined is monophyletic. Before, considerable disagreement existed concerning its proper circumscription (Windham 1993).
1. Fertile and sterile leaf blades very to moderately dissimilar, the (inner) fertile ones longer and narrower than the (outer) sterile ones. Fronds finely dissected, parsley-like, the ultimate segments almost linear (less than 0,5 cm wide). Sori superficial to submarginal. Pseudoindusium present or absent === 2
1. Fertile and sterile leaf blades similar to moderately dissimilar (in the latter case, ultimate segments much wider, usually at least 1 cm wide). Sori marginal. Pseudoindusium present === 3
2. Ephemeral annual. Pseudoindusium absent === Anogramma
2. Perennial. Pseudoindusium present, i.e. revolute margins of the fertile segments (native) === Cryptogramma
3. Rachis blackish. Pinnae petiolate, pentagonal or flabellate === 4
3. Rachis never blackish (green, straw-coloured or light brown). Pinnae sessile, lanceolate === Pteris
4. Pinnae flabellate, membranous. Margins of pinnae discontinuously revolute === Adiantum
4. Pinnae pentagonal, coriaceous. Margins of pinnae continuously revolute === Cheilanthes
Smith A.R., Pryer K.M., Schuettpelz E., Korall P., Schneider H. & Wolf P.G. (2006) A classification for extant ferns. Taxon 55(3): 705-731.
Windham M.D. (1993) Pteridaceae. In: Flora of North America Editorial Committee (ed.), Flora of North America north of Mexico, vol. 2. Oxford University Press, New York-Oxford: 122-186.